Dynamically adjustable multiphasic defibrillator pulse system and method

ABSTRACT

A dynamically adjustable multiphasic pulse system and method are provided. The dynamically adjustable multiphasic pulse system may be used as pulse system for a defibrillator or cardioverter.

PRIORITY CLAIMS/RELATED APPLICATIONS

This application claims priority under 35 USC 120 and is a continuationof U.S. patent application Ser. No. 15/484,055, filed Apr. 10, 2017 andtitled “Dynamically Adjustable Multiphasic Defibrillator Pulse SystemAnd Method” (now U.S. Pat. No. 9,855,440 issued on Jan. 2, 2018) that inturn claims priority under 35 USC 120 and is a continuation of U.S.patent application Ser. No. 14/303,541, filed Jun. 12, 2014 and titled“Dynamically Adjustable Multiphasic Defibrillator Pulse System AndMethod” (now U.S. Pat. No. 9,616,243) which in turn claims priorityunder 35 USC 120 and claims the benefit under 35 USC 119(e) to U.S.Provisional Patent Application Ser. No. 61/835,443 filed Jun. 14, 2013and titled “Dynamically Adjustable Multiphasic Defibrillator PulseSystem and Method”, the entirety of all of which are incorporated hereinby reference.

FIELD

The disclosure relates to medical devices and in particular to devicesand methods that generate therapeutic treatment pulses used in medicaldevices, such as cardioverters and defibrillators.

BACKGROUND

A primary task of the heart is to pump oxygenated, nutrient-rich bloodthroughout the body. Electrical impulses generated by a portion of theheart regulate the pumping cycle. When the electrical impulses follow aregular and consistent pattern, the heart functions normally and thepumping of blood is optimized. When the electrical impulses of the heartare disrupted (i.e., cardiac arrhythmia), this pattern of electricalimpulses becomes chaotic or overly rapid, and a sudden cardiac arrestmay take place, which inhibits the circulation of blood. As a result,the brain and other critical organs are deprived of nutrients andoxygen. A person experiencing sudden cardiac arrest may suddenly loseconsciousness and die shortly thereafter if left untreated.

The most successful therapy for sudden cardiac arrest is prompt andappropriate defibrillation. A defibrillator uses electrical shocks torestore the proper functioning of the heart. A crucial component of thesuccess or failure of defibrillation, however, is time. Ideally, avictim should be defibrillated immediately upon suffering a suddencardiac arrest, as the victim's chances of survival dwindle rapidly forevery minute without treatment.

There are a wide variety of defibrillators. For example, implantablecardioverter-defibrillators (ICD) involve surgically implanting wirecoils and a generator device within a person. ICDs are typically forpeople at high risk for a cardiac arrhythmia. When a cardiac arrhythmiais detected, a current is automatically passed through the heart of theuser with little or no intervention by a third party.

Another, more common type of defibrillator is the automated externaldefibrillator (AED). Rather than being implanted, the AED is an externaldevice used by a third party to resuscitate a person who has sufferedfrom sudden cardiac arrest. FIG. 10 illustrates a conventional AED 800,which includes a base unit 802 and two pads 804. Sometimes paddles withhandles are used instead of the pads 804. The pads 804 are connected tothe base unit 802 using electrical cables 806.

A typical protocol for using the AED 800 is as follows. Initially, theperson who has suffered from sudden cardiac arrest is placed on thefloor. Clothing is removed to reveal the person's chest 808. The pads804 are applied to appropriate locations on the chest 808, asillustrated in FIG. 10. The electrical system within the base unit 802generates a high voltage between the two pads 804, which delivers anelectrical shock to the person. Ideally, the shock restores a normalcardiac rhythm. In some cases, multiple shocks are required.

Another type of defibrillator is a Wearable Cardioverter Defibrillator(WCD). Rather than a device being implanted into a person at-risk fromSudden Cardiac Arrest, or being used by a bystander once a person hasalready collapsed from experiencing a Sudden Cardiac Arrest, the WCD isan external device worn by an at-risk person which continuously monitorstheir heart rhythm to identify the occurrence of an arrhythmia, tocorrectly identify the type of arrhythmia involved and then toautomatically apply the therapeutic action required for the type ofarrhythmia identified, whether the therapeutic action is cardioversionor defibrillation. These devices are most frequently used for patientswho have been identified as potentially requiring an ICD and toeffectively protect them during the two to six month medical evaluationperiod before a final decision is made and they are officially clearedfor, or denied, an ICD.

The current varieties of defibrillators available on the market today,whether Implantable Cardioverter Defibrillators (ICDs) or AutomaticExternal Defibrillators (AEDs) or any other variety such as WearableCardioverter Defibrillators (WCDs), predominantly utilize either amonophasic waveform or a biphasic waveform for the therapeuticdefibrillation high-energy pulse. Each manufacturer of defibrillators,for commercial reasons, has their own unique and slightly different takeon waveform design for their devices' pulses. Multiple clinical studiesover the last couple of decades have indicated that use of a biphasicwaveform has greater therapeutic value than a monophasic waveform doesto a patient requiring defibrillation therapy and that biphasicwaveforms are efficacious at lower levels of energy delivery thanmonophasic waveforms.

All of the current products that use a biphasic waveform pulse have asingle high-energy reservoir, which, while simple and convenient,results in severe limitation on the range of viable pulse shapes thatcan be delivered. Specifically, the second or Negative phase of theBiphasic waveform is currently characterized by a lower amplitudestarting point than the first or Positive phase of the Biphasicwaveform, as shown in FIG. 3. This is due to the partial draining of thehigh-energy reservoir during delivery of the initial Positive phase andthen, after inverting the polarity of the waveform so that the Negativephase is able to be delivered, there is only the same partially drainedamount of energy remaining in the energy reservoir. This lower amplitudestarting point constrains and causes the lower initial amplitude of theNegative phase of the waveform. The typical exponential decay dischargeis shown by the Positive phase of the waveform shown in FIG. 5 and howthe reservoir would have continued to discharge (if the polarity had notbeen switched) is shown as a dashed line in FIG. 5.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate a multiphasic waveform system with aplurality of independent subsystems each with its own energy reservoirand energy source;

FIG. 2 illustrates another embodiment of the multiphasic waveform systemwith two independent subsystems each with its own energy reservoir andenergy source;

FIG. 3 illustrates a typical H-bridge circuit;

FIG. 4 illustrates an H-bridge circuit in the multiphasic waveformsystem;

FIG. 5 illustrates a Biphasic pulse waveform where the negative phase ofthe waveform is smaller in amplitude than that of the positive phase ofthe waveform;

FIG. 6 illustrates a shape of a Biphasic pulse waveform that may begenerated by the systems in FIGS. 1 and 2 where the negative phase ofthe waveform is identical in amplitude to that of the positive phase ofthe waveform;

FIG. 7 illustrates a shape of Biphasic pulse waveform that may begenerated by the systems in FIGS. 1 and 2 where the negative phase ofthe waveform is larger in amplitude to that of the positive phase of thewaveform;

FIG. 8 illustrates a shape of Multiphasic pulse waveform that may begenerated by the systems in FIGS. 1 and 2 where the negative phases ofthe waveform are interlaced or alternated with those of the positivephases of the waveform, where the amplitudes of each phase steadilydecrease;

FIG. 9 illustrates a shape of Multiphasic pulse waveform that may begenerated by the systems in FIGS. 1 and 2 where the negative phases ofthe waveform are interlaced or alternated with those of the positivephases of the waveform, where the amplitudes of each phase remain thesame; and

FIG. 10 diagrammatically illustrates an example of a conventionaldefibrillator.

DETAILED DESCRIPTION OF ONE OR MORE EMBODIMENTS

The disclosure is particularly applicable to a multiphasic pulse systemfor an external defibrillator and it is in this context that thedisclosure will be described. It will be appreciated, however, that themultiphasic pulse system has greater utility since it may be used togenerate one or more pulses for other systems. For example, the pulsesystem may be used to generate therapeutic treatment pulses for othertypes of defibrillators, cardioverters or other systems. For example,the pulse system may be used to generate therapeutic treatment pulsesand then provide the pulses to a patient using paddles or pads. Whenused for defibrillation, the pulse system may generates the pulses anddeliver them to a patient through two defibrillation pads or paddles.

The multiphasic pulse system overcomes the limitation on the amplitudeof follow on phases of the pulse waveform by using two or morehigh-energy reservoirs and/or sources, such as the four shown in FIGS.1A and 1B. The pulse system 10 is not limited to any particular numberof energy reservoirs (such as capacitors) or energy sources (such asbatteries). The pulse system 10 may have a plurality or “n” number (asmany as wanted) subsystems 12, 14 that together can be utilized toprovide the various multiphasic waveforms, examples of which are shownin FIGS. 5-9 and described below. In the example implementation shown inFIG. 1A, there may be two sides, such as side A and side B as shown, andeach side may have one or more of the subsystems 12, 14 and eachsubsystem may generate a pulse (that may be a positive pulse or anegative pulse.) The two or more subsystems 12, 14 permit the system toshape the various characteristics of a positive phase of the waveformseparately from the shaping of the characteristics of the negative phaseof the waveform and vice versa. The above described functions may beaccomplished through the use of a fast switching high-energy/voltageswitch system as described below.

Each subsystem 12, 14 of each side, as shown in FIG. 1B, may have acontrol logic and heart rhythm sense component 20 (that is connected toa similar component on the other side by a digital control link 30 asshown in FIG. 1A) that may be also coupled to a high voltage switchingsystem component 22. The high voltage switching system component 22 maybe implemented using either analog circuits or digital circuits or evensome hybrid of the two approaches. Furthermore, the high voltageswitching system component 22 may be implemented through the use ofmechanical or solid-state switches or a combination of the two. As shownin FIG. 4, the high voltage switching system component 22 may beimplemented using one or more semiconductor circuits, such as theinsulated gate bipolar transistors. The high voltage switching systemcomponent 22 may be coupled to an energy reservoir 24 and the energyreservoir 24 may be coupled to a power source 26, such as a battery. Theenergy reservoir 24 may further comprise a reservoir 24A, such as forexample one or more capacitors or a capacitor array, and a high voltagegenerator 24B. The energy reservoir 24 may also be coupled, by a highvoltage return line 32 to the other side of the system as shown in FIG.1A. The high voltage return 32 electrically completes the circuit and ispresent in existing defibrillators, but in a slightly different formsince in the existing style of devices it is split into two parts: inthe form of the two leads which go from the main defibrillator device tothe internal or external surface of the patient.

The control logic and heart rhythm sense component 20 is well known inthe art and the component analyzes the ECG signals from the patient fortreatable arrhythmias and then chooses to shock the patient when atreatable arrhythmia is detected, along with guiding the operatorthrough both visual and audible means through this process when thedevice is of the external automated variety. The control logic and heartrhythm sense component 20 also may control and shape the therapeuticpulse as it is delivered from the energy reservoir and ensures that itis as optimal as possible for the individual patient. In theimplementations shown in FIGS. 1A and 2, the control logic and heartrhythm sense component 20 may generate the therapeutic pulse using theone or more groups of subsystems since each subsystem may have its owncontrol logic 20 (so that each of them can control just theportion/phase of the pulse/waveform that they deliver. This provides amuch higher level of control over what range of waveform shapes can beused/delivered, including many that are not possible with the existingdevices. This also provides better weight and size distribution, as wellas size and weight reductions, and the ability to have the devices lookradically different and be handled in very different ways—ones that aremuch more operator intuitive. The disclosed system also provides a muchhigher level of redundancy and fault mitigation for the deviceembodiments that use it.

In one implementation, each control logic in each subsystem may have acircuit that can be used to adjust the shape of each portion of thetherapeutic pulse. The circuit, may be for example, an array ofresistors of various strengths and switches so that one or more of theresistor may be selected (as an array of selectable resistors) that canoptimize and alter an RC constant of a subsystem's pulse phasegenerating circuitry in order to dynamically shape one or more pulsephases.

In some embodiments of the system, the system may provide for therecharging of individual energy reservoirs by the energy sources duringtimes (including inter-pulse times) that an individual energy reservoiris not selected for discharge as shown in FIGS. 1A and 2. This providesthe opportunity to interlace equivalent amplitude initial multiphasicpulses utilizing several different high energy reservoirs as shown inFIG. 9.

In one implementation, the system 10 may consist of two or morehigh-energy therapeutic pulse delivery sub-systems 12, 14 as shown inFIG. 2, such as Side A and Side B. In the implementation shown in FIG.2, the side A may deliver one or more of a Positive phase waveform ofthe Multiphasic therapeutic pulse and Side B may deliver one or more ofa Negative phase waveform of the Multiphasic therapeutic pulse. Thesubsystem in each side of the system in FIG. 2 may have the sameelements as shown in FIG. 1B and described above. As shown in FIGS. 1Aand 2, the subsystems may be coupled to the patient 16 by one or morehigh voltage leads and one or more sense leads wherein the high voltageleads deliver the therapeutic pulse and the sense leads are used todetect the heartbeat by the control unit.

The system 10 may either be pre-programmed to use a specific singlemultiphasic pulse shape, according to which one is shown to be mostefficacious in clinical lab testing/trials, or else it may select thebest one for a given purpose from a lookup table where they are listedaccording to their suitability for optimally resolving different typesof arrhythmia that are being screened for and identified or for thedifferent treatments as described above. Regardless, the system andmethod allows the use and application of a much wider range of pulseshapes than has been previously possible and this will allow the deviceswhich use this invention to keep up with clinical developments aswaveforms continue to be improved.

FIG. 3 illustrates a typical H-bridge circuit 300 and FIG. 4 illustratesan H-bridge circuit concept used in the multiphasic waveform system. Asshown in FIG. 3, an H-bridge circuit is a known electronic circuit thatenables a voltage, such as Vin, to be applied across a load, M, ineither direction using one or more switches (S1-S4) (seehttp://cp.literature.agilent.com/litweb/pdf/5989-6288EN.pdf that isincorporated by reference herein for additional details about theH-bridge circuit.) As shown in FIG. 3, the H-bridge circuit may have afirst portion 302 and a second portion 304 that form the completeH-bridge circuit.

As shown in FIG. 4, the H-bridge circuit may be part of the controlcircuits or switching systems shown in FIGS. 1-2. The load of theH-bridge circuit in the multiphasic system is the patient 16 to whichthe therapeutic pulse is going to be applied to provide treatment to thepatient. The treatment to the patient, depending on the power and/orenergy level of the therapeutic pulse may be for cardiac pacing,cardioversion, defibrillation, neurological therapy, nerve therapy ormusculoskeletal therapy. Each side of the multiphasic system maygenerate its energy as described above and an H-bridge circuit 400 maybe used to apply two (or more) unique energy sources to the single load.In the example shown in FIG. 4, each side of the system (such as side Aand side B shown in FIGS. 1A and 2) may have a portion 402, 404 of theH-bridge so that the multiphasic system has a complete H-bridge circuitthat is combination of portions 402, 404. The multiphasic system maythen be used to deliver the therapeutic pulse through defibrillationpaddles, such as Paddle A and Paddle B as shown in FIG. 4) to thepatient.

Each portion 402, 404 of the H-bridge has its own energy source, 1600VDC in the example in FIG. 4. In each portion of the H-bridge, theenergy source may be switched using switches 406, 408 to make contactwith the patient at a separate but specific time. The switches for eachportion may be part of the switching system shown in FIGS. 1-2. In theexample in FIG. 4, each portion may have two switches and each switchmay be a commercially available insulated-gate bipolar transistor(IGBT.) Each switch may be controlled by a separate trigger signal asshown to discharge the energy to the patient. This provides for the twoor more energy sources to discharge their energy to the load (patient)at a precise time, generating a resulting Biphasic discharge pulse orother therapeutic pulse shapes (examples of which are shown in FIGS.5-9) as defined for an application, or therapeutic condition.

In the system, a therapeutic pulse may comprise one or more positivepulses and one or more negative pulses. As shown in FIGS. 1A and 2, eachside (A & B) has one or more independent high-energy subsystems 12, 14so that the magnitude and the timing for each of the Positive & Negativephases of the Multiphasic therapeutic pulse are independent and cantherefore be independently controlled so as to provide a variety ofdifferent pulses as shown in FIGS. 5-9. FIG. 5 is typical of the currentBiphasic therapeutic pulses available in many defibrillators currentlyon the market today (with a positive pulse and negative pulse as shown)that may also be generated by the systems in FIGS. 1A and 2. FIG. 6illustrates a therapeutic pulse generated by the pulse system in whichthe magnitude of the Positive and Negative phases of the waveform areequal in starting amplitude. Furthermore, because each side or portionof the waveform generating circuit (subsystems A & B) are independent,the amplitude of the Positive phase of the waveform can be smaller inmagnitude than the Negative phase of the waveform, as illustrated inFIG. 7. Additionally, due to the independent nature of the two (or more)subsystems in the circuit, it is possible to alternate the Positive andNegative phases at intervals throughout the delivery of the Multiphasictherapeutic pulse as shown in FIGS. 8 and 9, or that the second (orlater) phase of the pulse can be of a measurably lower amplitude thanwould normally be deliverable from a single partially depleted energyreservoir. Further, each of the subsystems may have a dynamicallyvariable and selectable voltage output such that the amplitude of eachpulse phase can be individually controlled. In one implementation of thesystem, the therapeutic pulses in FIGS. 4-9 may be therapeuticdefibrillation or cardioversion pulses. In another implementation of thesystem, the therapeutic pulses in FIGS. 5-9 may be lower energytherapeutic pulses used in the treatment of neurological, nerve ormusculoskeletal conditions. Thus, the pulse generation system maygenerate pulse phases at any of a variety of power and energy levelsallowing for the use of the pulses for a variety of purposes such as incardiac pacing, cardioversion and defibrillation in addition toneurological, nerve or musculoskeletal therapies.

While the foregoing has been with reference to a particular embodimentof the invention, it will be appreciated by those skilled in the artthat changes in this embodiment may be made without departing from theprinciples and spirit of the disclosure, the scope of which is definedby the appended claims.

The invention claimed is:
 1. A multiphasic pulse generator, comprising:a plurality of subsystems wherein each subsystem has a power source andan energy reservoir; at least one of the plurality of subsystemsgenerates a first phase of a pulse that has a shape and is one of apositive phase of the pulse and a negative phase of the pulse; at leastone of the plurality of subsystems generates a second phase of the pulsethat has a shape and is an opposite polarity phase to the first phase ofthe pulse; and a switch element that switches between the subsystem thatgenerates the first phase of the pulse and the subsystem that generatesthe second phase of the pulse to generate a therapeutic pulse having atleast one positive phase and at least one negative phase.
 2. Thegenerator of claim 1, wherein each subsystem further comprises a circuitthat adjusts the shape of the phase of the pulse.
 3. The generator ofclaim 2, wherein the circuit includes an array of selectable resistors.4. The generator of claim 2, wherein the circuit includes an array ofselectable capacitors.
 5. The generator of claim 1, wherein the switchelement further comprises a high voltage switch element.
 6. Thegenerator of claim 5, wherein the high voltage switch element furthercomprises one or more semiconductor circuits.
 7. The generator of claim6, wherein the one or more semiconductor circuits further comprises oneor more insulated gate bipolar transistors.
 8. The generator of claim 1,wherein each subsystem further comprises control logic to control thegeneration of the phase of the pulse.
 9. The generator of claim 8,wherein each of the control logic further comprises a lookup table toselect the pulse shape.
 10. A method for generating a therapeutic pulse,comprising: providing a plurality of subsystems wherein each subsystemhas a power source and an energy reservoir; using one of the pluralityof subsystems to generate one or more positive phases for a pulse; usinga different one of the plurality of subsystems to generate one or morenegative phases for a pulse using a second power source and a secondenergy reservoir; and switching between the one or more positive phasesand the one or more negative phases to generate a therapeutic pulsehaving at least one positive phase and at least one negative phase. 11.The method of claim 10, further comprising adjusting a shape of each ofthe one or more negative phases and independently adjusting a shape ofeach of the one or more positive phases.
 12. The method of claim 10,further comprising individually selecting an amplitude of one or more ofthe one or more positive phases and one or more negative phases of thepulse.
 13. The method of claim 10, further comprising recharging theenergy reservoir when the energy reservoir is not being discharged. 14.The method of claim 10, further comprising recharging the second energyreservoir when the second energy reservoir is not being discharged. 15.The method of claim 10, further comprising alternating between the oneor more positive phases and the one or more negative phases whengenerating the therapeutic pulse.
 16. The method of claim 10, whereingenerating the therapeutic pulse further comprises selecting a shape ofthe therapeutic pulse using a lookup table.